ECOLOGY
** Watch “Symbiosis in the Sea” and “Defense in the Sea” video **
1.
Ecology – The study of the relationship between an organism and its physical and
chemical conditions of the environment. The word comes from the Greek root oikos,
meaning “house,” and the English suffix -ology, meaning “the study of.”
2.
Population - group of individuals of the same species that live together.
3.
Community - represents all the populations of organisms living in the same area.
4.
Ecosystem - composed of one or more communities, including the physical environment
of a specific area.
5.
Abiotic – The nonliving part of an environment, such as temperature, pressure, and
salinity
6.
Biotic – The living part of an environment that interacts with other organisms, such as
competing for living space, food, attracting mates, and interrelating in other ways.
7.
Predator - organism that eats another organism
8.
Prey - organism that is eaten by the predator.
9.
Symbiosis - refers to close living association between two species. Symbiosis types are:
a. Commensalism: where one species benefits from the relationship while the other is
not affected.
b. Parasitism: similar to predation in that one of the interacting species feeds on the
other. Parasites are generally much smaller than their hosts and usually live in a long
or continuous association with them rather than instantly devouring them.
c. Mutualism: relationship in which both organisms benefit.
10. Trophic levels – the classification of life
forms into two broad categories:
autotophs and heterotrophs. Each step in a
food chain is called a trophic level.
11. Food chain – food chain starts with a
species that eats no other species in the
web and ends at a species that is eaten by
no other species in the web.
12. Food web – also called food cycle; shows
“what eats what” feeding connections.
13. Detritus – Dead organic matter and the
decomposing organisms living among it;
considered the recycling bin of the ocean
ecosystem.
As flow of energy moves through the food chain and web, there is a 10-20% loss of energy.
Example: When a sea otter feeds on a sea urchin, it does not eat the hard outer layer or
spines. The energy bound up in that material is unusable to the next food-chain level. Each
consumer also gives off energy contained in their secretions and excrements. Those are also
lost to next level consumer. We can use ecological pyramid to illustrate.
Since there is less original energy in each level you move up, there are usually fewer
organisms in the level. Example: Less herbivore consumers than primary producers, less 1st
level carnivores than herbiovores, less 2nd level carnivores than 1st level, and so on.
PRIMARY PRODUCTIVITY
So how do we compare one ecosystem to another? The answer is in the food at the base of
the ecological pyramids. Since primary producers supply the energy (food) in an ecosystem,
scientists can measure the ecosystem's rate of production, or productivity, by studying the
ecosystem and rate of photosynthesis by producers living there.
What does this mean at a chemical level? When producers photosynthesize, they convert
carbon dioxide, water, and energy into organic matter plus oxygen. During photosynthesis,
the carbon from carbon dioxide is converted from inorganic to a useful organic form. This is
called carbon fixation. In other words, to make inorganic carbon useful to the ecosystem, it
is “fixed” into organic carbon. The solar energy taken in by the producers is stored within the
organic molecules in the form of simple sugars.
** Do carbon fixation experiment **
CARBON & NITROGEN CYCLES
As with nature, the basic elements of life recycle. Inorganic molecules are incorporated into
the components of living autotrophic organisms. These molecules are then transferred to
heterotrophic organisms when feeding on the autotrophic organisms. Finally, the molecules
are released back into the ecosystem when an individual dies and its body is broken down by
decomposers. Let's take a look at two of these cycles.
The carbon cycle is a relatively simple cycle in an ecosystem. Carbon dioxide (CO2) is an
atmospheric gas and is also found dissolved in water. This is the main source of carbon in
living systems. During photosynthesis, primary producers fix carbon dioxide and produce
simple sugars. These sugars are the main source of carbon for all other organisms in the
ecosystem. Respiration of that sugar by consumers and decomposers converts the organic
carbon compound back into inorganic carbon dioxide, which is then available for the
producers again.
In living organisms, nitrogen is not present in as large a quantity as carbon, but nitrogen
compounds such as DNA and amino acids are essential for life. The nitrogen cycle is
essential for making sure that there is enough nitrogen in an ecosystem so that these
compounds can be made.